1. Field of the Invention
The present invention relates in general to a claw device for transporting specimen plates, particularly those used for electron microscope specimens, and in particular, to a claw device for specimen plates used during the preparation of specimens which are cooled to low temperatures.
2. Description of the Prior Art
In the preparation of cooled electron microscope specimens, it is frequently necessary to transfer objects mounted on a specimen plate from a coolant, for example liquid nitrogen, into a microtome to produce freeze fractures. Alternatively, the specimen plate must be transferred into a vacuum unit for freeze drying and subsequent oblique sputtering. To effect the necessary transfers, a tool is needed which permits a secure engagement of the specimen plate to be transported without imparting any damage to the specimens.
It is known to use grip tongs for transporting specimens, this, however, requires a considerable amount of skill. Also known is a device which is designed as a gripper having holding claws and an actuating mechanism for extending the claws. A disadvantage of the prior device is that it is composed of a plurality of movable individual parts and, therefore, susceptible to trouble. More particularly, the contact pressure of the holding claws on the specimen plate is produced by a compression spring and the safe support of the plate depends on the state of the spring. After long service, for example, the spring may show signs of fatigue or even break completely.